Systems with high density packing of micromachines

ABSTRACT

Micromachine systems are provided. An embodiment of such a micromachine system includes a substrate that defines a trench. First and second microelectromechanical devices are arranged at least partially within the trench. Each of the microelectromechanical devices incorporates a first portion that is configured to move relative to the substrate. Methods also are provided.

BACKGROUND OF THE INVENTION Summary of the Invention

Briefly described, the present invention relates to micromachines. Inthis regard, embodiments of the invention may be construed asmicromachine systems. An embodiment of such a micromachine systemincludes a substrate that defines a trench. First and secondmicroelectromechanical devices are arranged at least partially withinthe trench. Each of the microelectromechanical devices incorporates afirst portion that is configured to move relative to the substrate.

Other embodiments of the invention may be construed as methods forforming arrays of micromachines. In this regard, an embodiment includesthe steps of providing a substrate and forming a trench in thesubstrate. First and second microelectromechanical devices are arrangedat least partially within the trench. Each of the microelectromechanicaldevices includes a first portion that is configured to move relative tothe substrate.

Other features and advantages of the present invention will becomeapparent to one with skill in the art upon examination of the followingdrawings and detailed description. It is intended that all such featuresand advantages be included herein within the scope of the presentinvention, as defined in the appended claims.

FIELD OF THE INVENTION

The present invention generally relates to micromachines and, morespecifically, to systems and methods that provide high density packingof micromachines on a substrate.

DESCRIPTION OF THE RELATED ART

Micromachines, such as microelectromechanical system (MEMS) devices, arebecoming prevalent in numerous applications. These devices are able toprovide mechanical functionality on an extremely small scale. Forexample, a typical micromachine can be formed on the scale of tens ofnanometers to millimeters.

Oftentimes, micromachines are formed on substrates, e.g., asemiconductor wafer. A single substrate can include hundreds ofmicromachines or more. The number of micromachines that are able to beprovided per unit area of substrate, i.e., the packing density of themicromachines, is influenced by several factors. For example, the sizeof the micromachines and spacing provided between adjacent micromachinesaffect the packing density of the micromachines.

Since there is a seemingly perpetual desire to increase the packingdensity of micromachines, there is a need for systems and methods thataddress this and/or other desires.

DESCRIPTION OF THE DRAWINGS

The present invention, as defined in the claims, can be betterunderstood with reference to the following drawings. The drawings arenot necessarily to scale, emphasis instead being placed on clearlyillustrating the principles of the present invention.

FIG. 1 is a schematic diagram depicting a portion of a substrateincluding a representative arrangement of micromachines.

FIG. 2 is a schematic diagram depicting the micromachines of FIG. 1.

FIG. 3 is a schematic diagram depicting a representative arrangement ofmicromachines.

FIG. 4 is a schematic diagram depicting a representative arrangement ofmicromachines.

FIG. 5 is a schematic diagram depicting a portion of a substrateincluding an representative arrangement of micromachines.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures wherein like reference numerals indicatecorresponding components throughout the several views, FIG. 1 depicts anembodiment of a micromachine system 100. As described in greater detailhereinafter, embodiments of the micromachine system of the presentinvention can employ various techniques for providing high densitypacking of micromachines.

In FIG. 1, micromachine system 100 includes multiple micromachines 110that are provided on a substrate 111. By way of example, substrate 111can be a semiconductor wafer. Each micromachine 110 incorporates amicromover component (“micromover”) 112. Micromovers 112 are adapted tomove relative to at least a portion of substrate 111. In otherembodiments of the invention, various types of micromachines other thanmicromovers can be used. However, in the description that follows,embodiments of the invention will be described with reference tomicromovers. This is done merely for ease of description and not for thepurpose of limitation.

Micromovers 112 preferably are spaced from each other so that adjacentmicromovers 112 do not interfere with each other. More specifically, ifadjacent micromovers were permitted to contact each other, either orboth of the micromovers could be inhibited from performing theirintended functions and/or could be damaged. Spacing between adjacentmicromachines is accommodated by arranging each micromover within acorresponding trench 116. Preferably, each trench is defined by materialof substrate 111. More specifically, the material of the substrate formsa longitudinal barrier 118 between adjacently disposed micromovers of arow 120 of micromovers. A transverse barrier 122 is formed betweenadjacently disposed micromovers of a column 124 of micromovers. Trenches116 can be formed by either removing material of the substrate in thedesired area of the trench, such as by etching, and/or by forming araised area about the desired area of the trench, such as by depositionof material.

In the embodiment depicted of FIG. 1, micromovers 112 are substantiallyretained within their respective trenches by flexures 130. Multipleflexures 130 engage each micromover 112. The flexures tend to maintain amicromover within its trench while permitting the micromover to move,e.g., micromover 112 moves relative to substrate 111. Representativeexamples of flexures include springs and micro-fabricated beams.

Each flexure 130 is affixed to an anchor 132. Anchor 132 can be formedas a component affixed to the substrate or as a portion of the materialof the substrate.

Micromachines can be fabricated by a variety of micromachiningprocesses. In a typical process, the device material is silicon that isprovided in the form of a wafer. The micromover, flexure, and anchorsystem are defined in the silicon wafer by a masking layer, which can beformed of a photoresist, for example. A deep silicon reactive ion etchmay be used to transfer the mask shape into the silicon wafer. A typicaletch depth may be 10 to 100 m. The etch depth is often set by anetch-stop layer that is provided in the silicon wafer beforemicromachining fabrication is begun. The etch-stop layer can be formedof silicon dioxide, for example. The etch-stop layer is used as asacrificial layer to facilitate the release of the micromover from thesubstrate. Release refers to a process by which constraints on the MEMSpart, e.g., the micromover, are removed. This allows the micromover tomove freely relative to the substrate. In the embodiment of FIG. 1, forexample, flexures and anchors serve to constrain the motion of thereleased micromover to the desired degrees of freedom.

An isotropic etch of the sacrificial layer is performed to remove thesacrificial material from about the micromachine components in desiredareas. The sacrificial layer may be 1 μm thick, for example. Theduration of the etch step will determine which structures are releasedfrom the substrate. For instance, the longer the etch time, the moresacrificial material typically is removed during the etch. By removingmore material during the etch, typically a larger structure, i.e., thestructure defined in the masking step, can be released. Given sufficienttime, the release etch can completely remove sacrificial material formedunderneath a micromover and its flexures. In contrast, anchors are notreleased by the etch. To prevent release of the anchors, the anchors areformed sufficiently wide so that they are not undercut by the etch to adegree that permits release.

Referring now to FIG. 2, it is shown that several discrete dimensionsaffect the packing density of the micromachines 110, i.e., the number ofmicromachines per unit area. More specifically, each micromachine 110exhibits a length (MX) and a width (MY), with MX and MY including boththe dimensions of the physical device and its operating range. Eachmicromachine 110 is spaced from an adjacent micromachine by a length(SX), i.e., SX is the distance between adjacent micromachines of thesame row, and a width (SY), i.e., SY is the distance between adjacentmicromachines of the same column. Thus, in the embodiment depicted inFIG. 2, the total area associated with a micromachine 110 is defined by:

MX+(2)(½ SX), in the X dimension; and

MY+(2)(½ SY), in the Y dimension.

An alternative embodiment of micromachine system 100 is depicted in FIG.3. As shown in FIG. 3, longitudinal barriers, which are shown in theembodiment of FIGS. 1 and 2, are not provided between adjacentmicromovers 110. In this configuration, an increased packing density ofthe micromachines is achieved compared to the embodiment of FIGS. 1 and2. More specifically, each micromachine 110 of FIG. 3 requires a lengthof MX1, i.e., in some embodiments, MX1<MX+(2)(½ SX).

Another embodiment of micromachine system 100 is depicted in FIG. 4. Asshown therein, separators 410 are provided between adjacently disposedmicromachines. The separators 410 are adapted to prevent direct contactof adjacent micromovers. Preferably, each separator 410 is formed as adistinct component, i.e., the separator is not formed entirely of thematerial of the substrate. For example, separator 410 could be amicro-fabricated beam that is similar to that of flexure 130.

In FIG. 4, anchors 420 are used to secure multiple flexures 130. Inparticular, each anchor 420 is arranged between an adjacent pair ofmicromovers and is used to affix at least one flexure from each of thepair of micromovers. Each anchor 420 also can secure one or moreseparators 410. Tn embodiments incorporating anchors for fixing multiplecomponents, such as flexures and/or separators, an increased packingdensity can be achieved. More specifically, in some embodiments,MX2<MX1<MX+(2)(½ SX).

In FIG. 5, micromachine system 100 includes multiple micromachines 502that are provided on a substrate 504. Micromachines 502 preferably arespaced from each other so that adjacent micromovers 506 do not interferewith each other. Flexures 508 of the micromachines are affixed toanchors. The anchors, being raised from a surface 510 of the substrate,define a trench 512 that is arranged about the anchors.

In FIG. 5, four types of anchors are depicted, i.e., anchors 514, 516,518 and 520. More specifically, anchors 514 are adapted to affix aflexure from a single micromover. Typically, such a micromover isarranged at a corner of the array of micromachines. In regard to anchors516, these anchors are adapted to affix flexures from at least twomicromachines. Since micromachine system 100 of FIG. 5 includes columns522 of micromachines, anchors 516 typically are provided only along theouter edge of a column of micromachines.

Anchors 518 also are adapted to affix flexures from at least twomicromovers. Anchors 518 typically are provided only along the outeredge of a row 524 of micromachines. Similar to anchors 516, anchors 518are adapted to affix flexures from at least two micromachines. However,unlike anchors 516, each of which engages flexures on opposing sides ofthe anchor, each anchor 518 typically engages the flexures along oneside of the anchor.

Anchors 520 typically are provided at locations other than the outerperiphery of an array of micromachines. As shown in FIG. 5, anchors 520are adapted to affix flexures from at least four micromovers. Inparticular, one side of an anchor is adapted to affix flexures ofadjacently disposed micromovers of a first row, and the other side ofthe anchor is adapted to affix flexures of adjacently disposedmicromovers of a second row.

Although not shown in FIG. 5, separators also can be provided between atleast some of the adjacently disposed micromovers of the micromachinesystem 100 depicted therein.

The foregoing description has been presented for purposes ofillustration and description. It is not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Modifications orvariations are possible in light of the above teachings. The embodimentor embodiments discussed, however, were chosen and described to providethe best illustration of the principles of the invention and itspractical application to thereby enable one of ordinary skill in the artto utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated.

For example, spacing between adjacently disposed micromachines may notbe required for micromachines that are intended to move together. Inthese embodiments, a further increase in packing density can be achievedby configuring these micromachines so that they engage each other. Allsuch modifications and variations are within the scope of the inventionas determined by the appended claims when interpreted in accordance withthe breadth to which they are fairly and legally entitled.

What is claimed is:
 1. A micromachine system comprising: a substratedefining a trench; a first microelectromechanical device arranged atleast partially within said trench, said first microelectromechanicaldevice including a first portion, said first portion being configured tomove relative to said substrate; and a second microelectromechanicaldevice arranged at least partially within said trench and adjacent tosaid first microelectromechanical device, said secondmicroelectromechanical device including a first portion, said firstportion being configured to move relative to said substrate.
 2. Themicromachine system of claim 1, further comprising: a first anchor fixedin position relative to said substrate, said first anchor beingconfigured to maintain said first portion of said firstmicroelectromechanical device at least partially within said trench; anda second anchor fixed in position relative to said substrate, saidsecond anchor being configured to maintain said first portion of saidsecond microelectromechanical device at least partially within saidtrench.
 3. The micromachine system of claim 1, further comprising: meansfor maintaining said first portion of said first microelectromechanicaldevice at least partially within said trench; and means for maintainingsaid first portion of said second microelectromechanical device at leastpartially within said trench.
 4. The micromachine system of claim 1,wherein said first portion of said first microelectromechanical deviceand said first portion of said second microelectromechanical device areconfigured to move independently of each other.
 5. The micromachinesystem of claim 1, further comprising: a separator disposed at leastpartially between said first microelectromechanical device and saidsecond microelectromechanical device, said separator being adapted toprevent said first microelectromechanical device from contacting saidsecond microelectromechanical device.
 6. The micromachine system ofclaim 1, further comprising: means for preventing said firstmicroelectromechanical device from contacting said secondmicroelectromechanical device.
 7. The micromachine system of claim 2,wherein: said first microelectromechanical device includes a firstflexure, said first flexure having a first end affixed to said firstanchor, said first flexure being affixed to said first portion of saidfirst microelectromechanical device, said first flexure being adapted todeform such that said first portion of said first microelectromechanicaldevice is capable of moving relative to said substrate; and said secondmicroelectromechanical device includes a first flexure, said firstflexure of said second microelectromechanical device having a first endaffixed to said second anchor, said first flexure of said secondmicroelectromechanical device being affixed to said first portion ofsaid second microelectromechanical device, said first flexure of saidsecond microelectromechanical device being adapted to deform such thatsaid first portion of said second microelectromechanical device iscapable of moving relative to said substrate.
 8. The micromachine systemof claim 5, wherein said separator is a micro-fabricated beam.
 9. Themicromachine system of claim 7, wherein said firstmicroelectromechanical device includes a second flexure, said secondflexure having a first end affixed to said second anchor, said secondflexure being affixed to said first portion of said firstmicroelectromechanical device; and wherein said secondmicroelectromechanical device includes a second flexure, said secondflexure of said second microelectromechanical device having a first endaffixed to said first anchor, said second flexure of said secondmicroelectromechanical device being affixed to said first portion ofsaid second microelectromechanical device.
 10. The micromachine systemof claim 7, further comprising: a third microelectromechanical devicearranged at least partially within said trench, said thirdmicroelectromechanical device including a first portion and a firstflexure, said first portion of said third microelectromechanical devicebeing configured to move relative to said substrate, said first flexureof said third microelectromechanical device having a first end affixedto said first anchor, said first flexure of said thirdmicroelectromechanical device being affixed to said first portion ofsaid third microelectromechanical device, said first flexure of saidthird microelectromechanical device being adapted to deform such thatsaid first portion of said third microelectromechanical device iscapable of moving relative to said substrate.
 11. The micromachinesystem of claim 8, further comprising: a separator disposed at leastpartially between said first microelectromechanical device and saidsecond microelectromechanical device, said separator being adapted toprevent said first microelectromechanical device from contacting saidsecond microelectromechanical device, said separator being adapted todeform in response to contact by said first portion of said firstmicroelectromechanical device and said first portion of said secondmicroelectromechanical device.
 12. The micromachine system of claim 8,wherein said first flexure of said first microelectromechanical deviceand said first flexure of said second microelectromechanical device aremicro-fabricated beams.
 13. The micromachine system of claim 10, furthercomprising: a fourth microelectromechanical device arranged at leastpartially within said trench, said fourth microelectromechanical deviceincluding a first portion and a first flexure, said first portion ofsaid fourth microelectromechanical device being configured to moverelative to said substrate, said first flexure of said fourthmicroelectromechanical device having a first end affixed to said firstanchor, said first flexure of said fourth microelectromechanical devicebeing affixed to said first portion of said fourthmicroelectromechanical device, said first flexure of said fourthmicroelectromechanical device being adapted to deform such that saidfirst portion of said fourth microelectromechanical device is capable ofmoving relative to said substrate.